1)a) option is the right answer.
Fins are used to increase heat transfer where heat transfer coefficient is low by increasing effective heat transfer area. This statement supports first option is the best choice.
2) d) option is correct
heat transfer rate Q is directly proportional to heat transfer coefficient(U), effective area(A) and temperature difference of cold and hot inlet. So, first three option does not convey anything about temperature difference of cold and hot inlet. Thus, we can not conlude anything from these statements about heat transfer. But fourth option says that equipment is new. Actually, old equipment’s heat transfer coefficient decreases due to fouling. Hence, new equipment has higher U. Hence, higher Q.
3) b) is the answer.
Steam economy is basically measurement of ratio of amount of water vaporized and amount of steam used. This parameter is defined only for judging the performance of evaportor. This eliminates rest options.
4) d) is the answer.
If feed temperature is low, we require more heat for heating the feed. Evaporator capacity is basically the amount of steam used to heat the feed for evaporation in 1hr. This eliminates all other options.